my 2004, at 6,000 like clockwork it comes on, even at partial throttle..why can't it just come on at say 3500, imagine the rush that would be...and what would happen to the 0-60 times with that kinda power and torque rush?

And if that is possible and it that is dooable, why hasnt' someone done it???3500(sooner than 6,000 rpm) is just a number, it could come on at 2500 or 4,000??? and why only at 6,000 rpm??? anyone have a theory or even by chance know???

 

Yeah. VTEC works by having two different cam profiles. One of them is optimized for low RPM's and the other for high RPM's. If Honda wanted VTEC to kick in at 3500 it they would have to design a cam profile that works well at those RPM's and replace one of the current profiles. They probably wouldn't be able to do that such that the upper end of our current RPM range wouldn't suffer. Chances are redline would be lowered and there would probably be less HP at whatever the new redline was. What Honda did was design a cam that had a low rpm profile that is well suited for the first 6k RPM's and then has a very aggressive cam profile for the top 3k RPM's. I'm sure they played with many combinations of profiles before deciding on the current combination in order to optimize the whole 9K range (8k for 2004 owners ).

 

It's designed that way for a reason. Under normal circumstances, adjusting the VTEC engagement point (by using a VAFC) would really be pointless, and I could even imagine it hindering performance.

Now of you have other stuff done to the car, or forced induction or whatever, then adjusting the engagement point would be logical.

The stock setup is cool though. You can be a around the town fuel efficient (relatively speaking) grocery hauler or just cruise with the top down, and the car is pretty good on gas.

And then if you want to open a can all you have to do is mash the gas, and the car becomes an entirely different beast. And if driven correctly, that beast doesn't go back into hiding until you tell it to.

 

Actually, there's some power to be had by altering the VTEC point a little lower (not as low as people believe), but it does good for autocrossing if you can keep it on the high cams a little longer before dropping back into the normal cams. The result is a more linear looking power delivery but there is a problem with this though...

1. Below the normal VTEC point, the car is on the weaker (normal) ignition map, so you're not really harnessing as much power as possible as if you're on the VTEC (high cam) ignition map.

2. It kills the VTEC kick that'd you'd normally feel. (IMHO, it takes away some of the fun)

Just my 2 cents.

 

Increasing the flow through the cylinders beyond what it can handle would not be a benefit but rather, a detriment. Sure, you could lower it a bit and you might feel some gains but you reach a break even point where lowering much more will cause the engine to be less efficient.
Ever stick your head out into the wind of a fast moving car? At certain angles, you get so much air forcing it's way into your airway, you actually can't breath.
Remember 4 barrel carbs? We used to have a little device that would connect up the secondary barrels so they opened immediately with the primaries when you mashed the gas. (They normally opened when manifold vacuum was just so.) Well, when you mashed the gas too fast, the engine would bog. Just too much of a good thing too fast. That is sorta like what our engine would do if you lowered the VTEC point too much.

 

Some people have had some success lowering VTEC to 5500-5700 but that's about as low as I've heard of. Certainly a different concept than lowering it to 3500.

 

I agree with everyone above, but I think Honda deliberately sets the VTEC engagement at least 200-300 RPMs higher than optimum. If they set VTEC engagement at the exact point where the two power curves crossed, there would be no VTEC sensation, just a smooth transition. I think Honda knows that a smooth VTEC transition would not be as marketable as it is when there is a distinct VTEC kick. Personally, I don't like the kick. I like the power curve to be as smooth as possible (most area under the curve).

 

It is set a couple hundred RPMs over optimum performance for gas mileage purposes. By dyno-tuning you can lower it a little bit to gain the optimum cross over rpms but going any lower than that it will just bog.

 

and actually, what Gernby said he prefers is actually better, a smooth Vtec transition. Smoother actually means you are making more power on the low cams rather than the car standing still and then lunging forward when you hit Vtec. People like the hard Vtec transition because it makes you feel like you are getting your "money's worth", have you ever felt the transition on I-Vtec motors? It is really smooth and you dont get that same kick.

 

Going to the high rpm cam sooner is likely to increase emissions and reduce mileage with minimal power benefit. Honda has many priorities to deal with when making these decisions.